Radiation spectrometer for RF breakdown detection in THz linear accelerators

The future of high energy particle physics and Xray light sources for biological and material research require miniaturized linear accelerators that at present cannot be qualified using existing methods. Such miniaturized linear accelerates will be instrumental in managing the cost of future accelerator facilities. There is presently no suitable diagnostic for ensuring RF breakdowns are minimized during the commissioning stage of these miniaturized linacs. In response to this shortcoming, RadiaBeam proposes to develop and build an automated singleshot gratingbased spectrometer working in the terahertz regime of these new miniaturized linacs. Such a device will be capable of measuring the presence of an RF breakdown event and will be used as a feedback mechanism in the commissioning of these linacs. Such grating spectrometers exist in the visible and infrared regimes but recent advances in materials science and detector technology make this scheme extendable to the regime of interest on a costeffective basis. A proofofprinciple spectrometer was developed and tested with bench top sources. After calibration and bench testing, the spectrometer was used in the successful qualification of a terahertz linac at Facility for Advanced Accelerator Experimental Tests (FACET) beamline at SLAC. The shortcomings of the proofofconcept device and potential additions were identified. Building on the success of the prooforprinciple demonstration, RadiaBeam will design and deploy a narrow band and wideband spectrometer for general THz instrumentation and terahertz linac qualification. The resulting spectrometers will be full commercial devices and will be tested at the THz test stand at the advanced Photon Source, and as an advanced RFBD diagnostic at MIT during the commissioning of a nextgeneration terahertz linac. The proposed spectrometer will allow advancement of miniaturized terahertz linacs, allowing miniaturization of many future DOE accelerator facilities. In addition, the oneofakind single shot spectrometer developed here can be used in a wealth of complimentary fields, including terahertz instrumentation, bunch length diagnostics, drug discovery, and homeland security. Key Words THz, terahertz, mmwave, spectrometer, singleshot, Wband, linac. RadiaBeam Systems seeks to build a commercial quality THz spectrometer necessary to qualify the next generation of miniaturized particle accelerators. The spectrometer has additional applications in biology, drug discovery, security, and general instrumentation while serving the DOE mission of basic science.